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From:   Anton Altaparmakov <anton@tuxera.com>
To:     Deepa Dinamani <deepa.kernel@gmail.com>
CC:     OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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Subject: Re: [PATCH 03/20] timestamp_truncate: Replace users of
 timespec64_trunc
Thread-Topic: [PATCH 03/20] timestamp_truncate: Replace users of
 timespec64_trunc
Thread-Index: AQHVRrCO7mUMDQahbUu7RSH43rBZCqbjOCQAgABUboA=
Date:   Tue, 30 Jul 2019 22:28:33 +0000
Message-ID: <5340224D-5625-48A6-909E-70B24D2084BC@tuxera.com>
References: <20190730014924.2193-1-deepa.kernel@gmail.com>
 <20190730014924.2193-4-deepa.kernel@gmail.com>
 <87d0hsapwr.fsf@mail.parknet.co.jp>
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Hi Deepa,

> On 30 Jul 2019, at 18:26, Deepa Dinamani <deepa.kernel@gmail.com> wrote:
> 
> On Tue, Jul 30, 2019 at 1:27 AM OGAWA Hirofumi
> <hirofumi@mail.parknet.co.jp> wrote:
>> 
>> Deepa Dinamani <deepa.kernel@gmail.com> writes:
>> 
>>> diff --git a/fs/fat/misc.c b/fs/fat/misc.c
>>> index 1e08bd54c5fb..53bb7c6bf993 100644
>>> --- a/fs/fat/misc.c
>>> +++ b/fs/fat/misc.c
>>> @@ -307,8 +307,9 @@ int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
>>>              inode->i_atime = (struct timespec64){ seconds, 0 };
>>>      }
>>>      if (flags & S_CTIME) {
>>> -             if (sbi->options.isvfat)
>>> -                     inode->i_ctime = timespec64_trunc(*now, 10000000);
>>> +             if (sbi->options.isvfat) {
>>> +                     inode->i_ctime = timestamp_truncate(*now, inode);
>>> +             }
>>>              else
>>>                      inode->i_ctime = fat_timespec64_trunc_2secs(*now);
>>>      }
>> 
>> Looks like broken. It changed to sb->s_time_gran from 10000000, and
>> changed coding style.
> 
> This is using a new api: timestamp_truncate(). granularity is gotten
> by inode->sb->s_time_gran. See Patch [2/20]:
> https://lkml.org/lkml/2019/7/29/1853
> 
> So this is not broken if fat is filling in the right granularity in the sb.

It is broken for FAT because FAT has different granularities for different timestamps so it cannot put the correct value in the sb as that only allows one granularity.  Your patch is totally broken for fat as it would be immediately obvious if you spent a few minutes looking at the code...

Best regards,

	Anton

> 
> -Deepa


-- 
Anton Altaparmakov <anton at tuxera.com> (replace at with @)
Lead in File System Development, Tuxera Inc., http://www.tuxera.com/
Linux NTFS maintainer